Austin Lake Dam
Kalamazoo County Drain Commission
Kalamazoo County Drain Commission repairs and improves a nearly-failing dam.
When the Austin Lake Dam nearly failed in 2005, the KCDC hired P&N to conduct an investigation, make recommendations for temporary repairs, and design long-term system improvements. The dam is an integral part of the Austin Lake Consolidated Drain, located in the City of Portage, Schoolcraft Township, and Pavilion Township.
P&N found that lake water was flowing under the dam foundation and coming up around the joints between the dam foundation, the concrete spillway, and the headwall. A large sinkhole had developed adjacent to the front face of the dam and was conveying water under the dam, causing much of the supporting soil to erode away.
To immediately stabilize the dam, the sinkhole was filled with a combination of stone and bentonite, and then backfilled with stone. A large tarp was spread across the channel bottom from the dam face upstream and then covered with stone to reduce the flow of lake water under the dam. Temporary weirs were set in front of the culverts to raise the water level downstream of the dam. These efforts successfully stopped and minimized water flow under the dam as a temporary fix.
P&N then planned and designed system improvements and prepared an assessment roll and computation of cost. The project had four components:
- A new 51-foot-wide Austin Lake Dam was designed and constructed, with sheet piling and solder piles, six eight-foot-wide-weirs, sheet pile seawalls (approximately 50 feet in length), and washed stone rip rap. The existing concrete dam was also removed.
- A 30,000-square-foot filtration basin was created to remove sediment in the drain. It includes 10,000 square feet of created wetland and 125+160+30 feet of piping and control structures.
- A 42-inch culvert was replaced. This phase included excavation, tree removal, and restoration.
- Other maintenance was performed, including the removal of fallen trees, uprooted stumps, and other obstructions in the channel.
Normal lake levels were maintained at Austin Lake throughout the project, in accordance with MDEQ soil erosion and sedimentation control requirements.
Project Manager Jim Hegarty, PE, (616) 364-8491